Risk factor analysis for infection and bleeding after lateral decubitus percutaneous nephrolithotomy

This study aimed to explore the risk factors for infection and bleeding after lateral decubitus percutaneous nephrolithotomy procedures to prevent their occurrence and improve surgical outcomes. A retrospective analysis was conducted on 356 patients who underwent lateral decubitus percutaneous nephrolithotomy for the treatment of kidney stones and upper ureteral stones from January 2015 to August 2022. Among them, 290 patients had complete clinical data. General clinical data, perioperative data, and stone characteristics were collected for each patient. Univariate and multivariate logistic regression analyses were performed to identify risk factors for infection and bleeding after lateral decubitus percutaneous nephrolithotomy. The postoperative infection rate after lateral decubitus percutaneous nephrolithotomy was 19.31%, and the postoperative bleeding rate was 12.07%. Independent risk factors for postoperative infection were multiple stones (P < .001), stone size (P < .001), and stone co-infection (P = .012). Independent risk factors for postoperative bleeding were multiple stones (P = .008) and stone size (P = .014). Multiple stones, stone size, and stone co-infection are independent risk factors for postoperative infection after lateral decubitus percutaneous nephrolithotomy. Multiple stones and stone size are independent risk factors for postoperative bleeding after lateral decubitus percutaneous nephrolithotomy.


Introduction
Upper urinary tract stones are a common condition affecting individuals of all ages and are prevalent worldwide. [1]4] The global prevalence of kidney stones is approximately 1%, but it may be higher in certain industrialized countries. [5,6]ommon treatment methods for kidney stones include extracorporeal shock wave lithotripsy, ureteroscopy, percutaneous nephrolithotomy (PCNL), and a few open surgical procedures. [7]10][11][12][13] Although PCNL has shown good efficacy in treating kidney and upper ureteral stones, there are potential risks of postoperative complications due to the complexity of stone diseases and surgical factors, resulting in a complication rate ranging from 3% to 83%. [14,15]Postoperative infection is a common complication of PCNL, with reported incidence rates ranging from 2.8% to 60%. [7,9,16]While most infections can be managed conservatively, 0.9% to 4.7% of patients may develop sepsis. [9,17]Postoperative bleeding is also a frequent complication, with reported incidence rates ranging from 0% to 45%. [7,9,18,19]Although most cases of bleeding can be managed conservatively, severe bleeding requiring renal artery embolization occurs in approximately 0.8% of cases. [20]dentifying risk factors for postoperative infection and bleeding after PCNL is essential to take proactive measures and reduce their occurrence.This study aims to provide clinical reference for diagnosing and treating patients undergoing lateral decubitus PCNL by exploring the risk factors associated with postoperative infection and bleeding.

The authors have no funding and conflicts of interest to disclose.
The datasets generated during and/or analyzed during the current study are not publicly available, but are available from the corresponding author on reasonable request.

Study population
A total of 356 patients with kidney or upper ureteral stones underwent lateral decubitus PCNL at Beijing University First Hospital-Miyun Hospital from January 2015 to August 2022.Among them, 290 patients had complete clinical data.The patients' demographic characteristics, stone features, and surgical outcomes were collected (Fig. 1).
The patients were divided into infection and non-infection groups based on the results of urine culture within 1 week after the PCNL procedure.The infection group had positive urine culture (>10 5 cfu/mL), indicating urinary tract infection.The non-infection group had negative urine culture.
The patients were also divided into bleeding and non-bleeding groups based on the postoperative decrease in hemoglobin levels.The bleeding group had a decrease in hemoglobin of 20 g/L or more, while the non-bleeding group had a decrease in hemoglobin of <20 g/L.Hemoglobin decline (g/L) = preoperative hemoglobin volume − hemoglobin volume on the first day after surgery.
Inclusion criteria were as follows: Patients with kidney stones or upper ureteral stones confirmed by ultrasound, intravenous pyelography, or CT examination; PCNL performed in the lateral decubitus position; Patients with complete data.
Exclusion criteria were: Patients with abnormal coagulation function; Patients with cardiac or pulmonary dysfunction unable to tolerate surgery; Patients unable to cooperate with the study.
The clinical variables included in this study were gender, age, body mass index, diabetes, hypertension, coronary artery heart disease, stone size, lesion side, stone location, multiple stones, puncture site, channel type, number of channels, operative time, intraoperative blood loss, preoperative heart rate, intraoperative heart rate, mode of anesthesia, and stone co-infection.Univariate and multivariate logistic regression analyses were used to analyze independent risk factors for postoperative infection and bleeding after lateral decubitus PCNL.

Surgical technique
After successful anesthesia, the patient was placed in the Lithotomy position, and routine disinfection and draping were performed.A cystoscope was used to examine the bladder mucosa and bilateral ureteral orifices, and an F6 ureteral catheter was inserted into the affected-side ureter under the guidance of a nickel-titanium alloy guidewire.The ureteral catheter was connected to normal saline to create "artificial hydronephrosis."Subsequently, the patient was switched to the lateral decubitus position.Under ultrasound guidance, a 1-time puncture needle was used to puncture the renal calyx.A safety wire was left in place, and a skin incision of approximately 0.8 cm was made.The renal access tract was dilated step by step to F16 using a fascial dilator from the sheath set, and a skin sheath was left in place.The nephroscope was introduced into the renal cavity for observation, and after identifying the stones, fragmentation and retrieval were performed.A 14F nephrostomy tube was placed after completing the procedure.

Statistical analysis
Data management was performed using Microsoft Excel (2019 version), and statistical analyses were performed using SPSS version 22.0.Descriptive statistics were presented as mean ± standard deviation for normally distributed variables and as median (range) for skewed variables.Student t test was used for normally distributed continuous variables, and the Mann-Whitney U test was used for non-normally distributed continuous variables.Fisher exact probability test was used for categorical variables.Univariate and multivariate logistic regression analyses (P < .05)were used to analyze independent risk factors for postoperative infection and bleeding.

Incidence of infection and bleeding after lateral decubitus PCNL
The demographic data, stone characteristics, and surgical outcomes of the patients are presented in Table 1.Patients ranged in age from 20 to 88 years, with an average age of 51.72 years.There were 179 male and 111 female patients.Among them, 243 patients had unilateral kidney stones, and 47 had bilateral stones.Multiple stones were observed in 69 cases, while 221 cases had a single stone.The average surgical duration was 115.31 ± 49.67 minutes, and the mean intraoperative blood loss was 19.25 ± 22.19 mL.After the procedure, 56 patients developed postoperative infections, resulting in an infection incidence of 19.31%.Additionally, 35 patients experienced postoperative bleeding, leading to a bleeding incidence of 12.07%.

Analysis of risk factors for postoperative infection following lateral decubitus PCNL
Clinical data of patients in the infected and non-infected groups after lateral decubitus PCNL are shown in Table 2.The average stone size was 3.41 ± 0.89 cm in the infected group and 2.75 ± 0.99 cm in the non-infected group, with a significant difference between the 2 groups (P < .001).The infected group had a longer average surgical duration (140.98 ± 71.734 minutes) compared to the non-infected group (109.14 ± 39.901 minutes), with a statistically significant difference (P < .001).

Analysis of risk factors for postoperative bleeding following lateral decubitus PCNL
Clinical data of patients in the postoperative bleeding and non-bleeding groups after lateral decubitus PCNL are presented in Table 4.The average stone size was 3.14 ± 0.95 cm in the bleeding group and 2.82 ± 0.99 cm in the non-bleeding group, with a significant difference between the 2 groups (P = .002).The bleeding group had a higher mean intraoperative blood loss (27.86 ± 18.76 mL) compared to the non-bleeding group    (18.07 ± 22.48 mL), with a statistically significant difference (P = .014).The bleeding group also had a longer average surgical duration (139.89 ± 53.65 minutes) compared to the non-bleeding group (111.92 ± 47.73 minutes), with a statistically significant difference (P = .002).Multiple stones were more prevalent in the bleeding group (P < .001).Univariate and multivariate logistic regression analyses indicated that multiple stones (P = .008)and stone size (P = .014)were independent risk factors for postoperative bleeding following lateral decubitus PCNL (Table 5).

Discussion
In recent years, with the advancement of surgical techniques, minimally invasive surgical methods have seen rapid development.PCNL is a minimally invasive and highly effective approach for treating kidney and upper ureteral stones.22][23] Although the incidence of complications related to PCNL has decreased significantly due to improvements in surgical techniques and pre-and perioperative monitoring, the occurrence rates still range from 3% to 83% for various complications. [14,17,24,25]Postoperative infection and bleeding are the most common complications.In our study, the incidence of postoperative infection was 19.31%, and postoperative bleeding occurred in 12.07% of cases.Oner et al [21] reported a postoperative bleeding rate of 12.6% with a need for arterial embolization in 0.4% of cases.Kuldeep Sharma et al [9] found a postoperative infection rate of 11.4%, with 1.5% of patients progressing to sepsis.Lorenzo Soriano et al [25] reported a postoperative infection rate of 14.8% after PCNL.Our study infection and bleeding rates were similar to previous research, and the incidence of postoperative infection and bleeding was higher.Thus, identifying potential risk factors influencing infection and bleeding rates and adopting proactive measures to reduce these rates are essential and meaningful.
In this study, it was found that stone size, surgical duration, hypertension, stone location, lesion side, multiple stones, number of channels, and stone co-infection showed statistical differences between the infected and non-infected groups.Among them, multiple stones, stone size, and stone co-infection were identified as independent risk factors for postoperative infection following lateral decubitus PCNL.Similar results were obtained in the study by Lorenzo Soriano et al, [25] where larger and more complex stones required more intricate surgical procedures, leading to longer surgical durations and an increased risk of infection.Kuldeep Sharma et al [9] found a significantly higher rate of postoperative fever and infection in patients with infected stones compared to sterile stones, likely due to the release of high concentrations of endotoxins during the treatment of infected stones.Multiple stones may lead to residual fragments, and in some cases, multi-tract PCNL is needed, making the procedure more complex and possibly contributing to postoperative infection. [26]Therefore, preoperative antibiotic prophylaxis and even staged PCNL with the placement of a double-J stent in these patients could be considered.Additionally, special attention should be paid to controlling intra-renal pressure during surgery to reduce the incidence of postoperative infection.
In this study, stone size, intraoperative blood loss, surgical duration, and multiple stones showed statistical differences between the bleeding and non-bleeding groups.Single-factor and multi-factor logistic regression analyses identified multiple stones and stone size as independent risk factors for postoperative bleeding following lateral decubitus PCNL.Daniel A. Wollin et al [27] also found that stone size influenced postoperative bleeding in their research.Similar to postoperative infection, larger stones and multiple stones make the surgical procedure more challenging, leading to longer surgical durations, and patients with thicker renal cortexes and longer tracts may be more prone to bleeding. [28,29]revious studies have found a correlation between multiple tract punctures and postoperative infection and bleeding, as multiple tracts may introduce more infectious agents and increase the risk of bleeding.However, in our study, no significant association was found between multiple tract punctures and postoperative infection, consistent with some previous research. [9,11,30]Ronald A. et al mentioned that insulin-dependent diabetes involves immunosuppressive pathology and may be a risk factor for postoperative infection, but this study did not find a significant association between insulin-dependent diabetes and postoperative infection. [31]ble 5 Univariate and multivariate logistic regression analysis for bleeding.Our study has certain limitations.It is a retrospective study, and some data on factors affecting postoperative infection and bleeding were missing.Moreover, being a single-center study, there may be some bias.Therefore, we plan to conduct a multi-center prospective study on risk factors for postoperative complications after PCNL to more accurately analyze the factors influencing the occurrence of complications.

Conclusion
In this study, the incidence of postoperative infection and bleeding following lateral decubitus PCNL was found to be similar to previous research, and both were relatively high.Multiple stones, stone size, and stone co-infection were identified as independent risk factors for postoperative infection, while multiple stones and stone size were identified as independent risk factors for postoperative bleeding following lateral decubitus PCNL.

Figure 1 .
Figure 1.Flow chart of inclusion and exclusion of the study.

Table 1
Basic characteristics of the patients.
BMI = body mass index, CHD = coronary artery heart disease.

Table 2
Baseline data of infected group and non-infected group.
BMI = body mass index, CHD = coronary artery heart disease.

Table 3
Univariate and multivariate logistic regression analysis for infection.
BMI = body mass index, CHD = coronary artery heart disease.

Table 4
Baseline data of bleeding group and non-bleeding group BMI = body mass index, CHD = coronary artery heart disease.www.md-journal.com